In the manufacture of nuclear fuel material, an intermediate product, ammonium diurinate (ADU) is formed during the conversion of uranium hexafloride to uranium dioxide. During this conversion process, the ammonium diurinate is dewatered in a centrifuge. After dewatering, the ammonium diurinate is partially rewetted and then held in a stirred surge tank as a slurry. Afterwards, the ammonium diurinate slurry is transported by a positive displacement pump to a dryer for solidification.
In the manufacturing process, a positive displacement pump having a shaft driven by a pneumatic driver is used. In one prior art type of pneumatic driver, air is injected alternately on two sides of a piston in a single cylinder. The piston axially strokes the pump shaft creating the positive displacement in the pump necessary for pumping the slurry. A pneumatic driver has been found desirable because of its simplicity and resistance to corrosion and abrasion. The manufacturing of nuclear fuel occurs in a corrosive and abrasive environment. Uranium is very corrosive and abrasive and small dust particles gather on moving parts and the uranium dust particles tend to wear the mechanical parts quickly. Additionally, nitric acid commonly is used in the manufacturing process and tends to wear the seals and bearings. As a result, it has been found desirable to use means such as a pneumatic driver which is simple in construction and efficient for driving a positive displacement pump when pumping an ammonium diurinate slurry.
During manufacturing of the nuclear fuel material, it has been found that the bearings of the positive displacement pump shaft wear from the continual work of pumping the corrosive and abrasive ammonium diurinate slurry. When the pump bearings wear, the pump shaft is subjected to greater radial movement. As a result of the increased radial movement of the pump shaft, the seals surrounding the pump shaft sometimes wear allowing some leakage of the ammonium diurinate onto the pump shaft. Any nominal amount of ammonium diurinate leaking on to the pump shaft typically may not be a problem. However, if air is blown onto the shaft, such as resulting from air leaking from the pneumatic driver which actuates the pump, the ammonium diurinate is blown into the atmosphere and mixes with the air to become a health hazard to workers. Often, the greater radial movement of the pump shaft wears the bearings of the pneumatic driver shaft and causes an increased radial movement of the driver shaft. This results in failure of the atmosphere seal in the pneumatic driver and as a result, air leaks past the atmosphere seal. This leaking air typically is blown onto the pump shaft and then blows the radioactive ammonium diurinate positioned on the shaft. As a result, a health hazard ensues. It is therefore more desirable to provide a pneumatic driver which does not use a piston for driving a shaft but makes use of an expandable air bladder and the like from which air may not leak such as around a piston and where the air bladder is expandable for moving a driving shaft forward.
It is therefore an object of this invention to provide a pneumatic driver which overcomes the deficiencies of the prior art.
It is another object of this invention to provide a pneumatic driver which uses air bladder expansion means for engaging and moving a shaft between an extended driving position and a retracted position for operating a positive displacement pump and the like.
It is another object of this invention to provide a pneumatic driver which is constructed to provide some freedom of lateral movement to the driver shaft without adversely affecting performance of the driver or allowing leakage of air.